Total hip arthroplasty and total arthroplasty have become increasingly useful methods of treating hip and knee joint disease. While great progress has been made in extending the life of prosthetic orthopedic implants, it is still necessary, in some cases, to perform revision surgeries which require the removal of already implanted hip and knee joint prosthetic components. Each prosthetic removal should avoid damage to the surrounding soft tissue and bone while conserving as much bone as possible. Current procedures do not control damage precisely.
Such removal of prosthetic implants requires the loosening of the implants which are fixed in the femur either by bone cement or ingrown tissue which fills porous surfaces on an implant designed for non-cemented attachment. A hammer and chisel are typically used to split the bone to loosen the implant causing trauma to the femur and complicating the procedure in both interval and complexity. The osteotome is another typically used tool to sever the interconnection between the typically metallic prosthesis and surrounding tissue or bone cement. Such a procedure is time consuming and tedious and runs the risk of damaging the femur when removing a femoral component from the intramedullary canal of a femur.
Recently there has been proposed a new procedure for removing a femoral prosthesis that removes a minimum of bone. A Stryker® Precision™ Oscillating Tip Saw is a surgical tool that is powered by a hand piece that houses a motor and the complimentary controlled circuit that regulates the actuation of the motor. This saw has a static planar guide bar that extends forward (distally) from the hand piece and has a planar saw blade. Typically the most forward or distal end of the saw blade is formed with teeth for cutting hard tissue against which the blade is applied. A drive mechanism internal to the handpiece transfers the power developed by the motor to the blade. More particularly, the drive mechanism converts the rotary motion produced by the output shaft of the handpiece moves the blade in an oscillatory, back-and-forth pattern in the plane in which the blade is aligned. Consequently, when the Precision™ saw is actuated, the blade teeth move in back-and-forth pattern against the hard tissue or bone to which the teeth are applied. As a consequence of this motion and the forward pressure applied by the surgeon holding the saw, the teeth cut and separate the hard tissue or bone from the implant tissue ingrowth surfaces.
In order to ensure that the proper cut lines are formed in the bone, the surgeon typically first mounts a cutting guide, sometimes called a jig, to the bone adjacent to the location where the cut is to be made. One type of cutting guide is in the form of a block formed with a precisely shaped set of slots. The slots define the lines along which the bone is to be cut. The surgeon then performs a surgical procedure by sequentially inserting the saw blade in the slots. Once the blade is inserted in a slot, the saw is actuated. In this manner, the surgeon is able to cut the bone or hard tissue along the precisely defined lines along which the bone is to be separated.
A saw of this type is disclosed in U.S. Patent Publication No. 2006/0009796 the disclosure of which is incorporated herein by reference. The saw disclosed therein is used by actuating a motor internal to the hand piece. The drive assembly transfers the power developed by the motor to the drive rod so that the rod simultaneously engage in a back-and-forth reciprocating motion in opposite directions. The drive rods, in turn, transfer the reciprocating motion to the saw blades so that the blade teeth move in a back-and-forth or side-to-side oscillating motion.